Molds for plastic blowing machines



Oct. 22, 1957 R. BOTTLEMAN 2,810,160

MOLDS FOR PLASTIC BLOWING MACHINES Filed Oct.' 5. 1953 United States Patent MOLDS FOR PLASTIC BLOWING MACHINES Ray Bottleman, Fitchburg, Mass., assignor to Great American Plastics Company, Fitcllburg, Mass., a corporation of Massachusetts Application October 20, 1953, Serial No. 387,130

2 Claims. (Cl. 18-42) The present invention relates to molds generally having two mold halves, and the object of the invention is to devise a mold particularly adapted for receiving a blank which consists of a hot plastic tube closed at both ends. When the mold halves are brought together after insertion of the hot closed plastic tube blank, and even before such action, a major problem exists in that with relatively thin wall blanks the latter sag and blow unevenly as to wall thickness. The blowing is effected, in the present embodiment, by means of a hollow needle connected to one of the mold halves and which, as the molds are closed, penetrates the tubular blank, air being forced through the needle for expanding the walls of the tubular blank and bringing them into conformity with the interior mold wall.

By the present invention, simple and effective means are provided in overcoming the problem hereinabove mentioned, the said means having been obtained after much trial and error and through discovery of a principle, i. e., that if one end of the tubular blank is penetrated and held by one or more needles, abnormal sagging of the tubular blank is prevented.

The invention will be described with reference to the accompanying drawing, in which:

Fig. 1 is a view in vertical section showing two mold halves separate, a tubular blank deposited therein and having needle penetration, the needle support being the lower mold half;

Fig. 2 is a view similar to Fig. 1 showing molds closed and the position of the elements after a blowing operation;

Fig. 3 is a plan view of the lower mold half; and

Fig. 4 is an end view of two molds, with the needles in position, the plastic tube blank end not being shown.

Referring to the drawing, the embodiment therein illustrated consists of a lower mold half 1 having a cavity 2 which at the right hand end terminates with a narrow wall 1x, an interior of the wall is shown in Figs. 1 and 2, and needle 3. As illustrated in Figs. 3 and 4, a plurality of needles are preferably employed.

As shown more particularly in Fig. 4, each mold at its end is cut away exterior the narrow wall 1x, hereinafter termed the pinching wall.

The upper mold half 4 is formed at the right of its cavity 5 with a narrow pinching wall 6, and exterior thereof the metal may be cut away to enable clearance for the needle or needles.

Each of the mold cavities is provided with a neck forming portion for a bottle as shown at 6x for the upper mold half and at 7 for the lower mold half, and in Fig. 1 there has been deposited a plastic tube blank which is closed at both ends and which will be hot and expansible when thus deposited in the mold.

Before the plastic tube blank is inserted in the mold, its halves will be widely separated when automatic means are employed for transferring the tube blank from a point at which it is formed from a tubular extrusion,

7 O and usually the hot plastic tube blank will be dropped onto the lower mold half, so that the needles 3 will pene- 2,810,160 Patented Oct. 22, 1957 ice trate the end of the tube blank exterior the pinching walls 1x and 6. Thereupon the mold halves are moved together and a hollow needle 8 will penetrate the hot plastic tube blank, and air for blowing the blank into a shape conforming to the interior walls of the mold will be admitted through a duct shown by dotted lines at 9.

Customarily the molds will be cooled, and in some cases they are water jacketed, such method of cooling not being shown in the drawing. By such cooling the blown article will become rigidified and the molds may then be opened and the article discharged therefrom.

When the mold halves are brought together, pinching walls 1x and 6 will bring the opposed walls of the hot plastic tube blank together and they will be fused. The needle penetrated axis end shown at 10, Fig. 2, will be retained exterior of the mold cavity, and the pinching walls 1x and 6 so designed as to cut oif such axis at the final closing movement of the mold halves.

It will be understood that various modifications may be made in the form and arrangement of the elements illustrated in the drawing without departing from the spirit of the invention.

Thus if the mold halves are supported vertically and the hot plastic tube blank is gravitationally dropped between the mold halves whilst they are separated the required degree, the needles 3 may be at such an angle, for example a sharp angle, as to catch and penetrate the lower end of the tube blank toward the end of its falling motion. Also both of the mold halves may carry one or more penetrating needles if desired. In Fig. l by dotted lines at 11 there is indicated two of such inclined needles.

Having described my invention, what I claim and desire to secure by Letters Patent is:

l. A mold assembly for blowing machines which consists of a mold adapted to blow closed hot plastic tube blanks consisting of two mold halves each having a cavity complementary with the second mold half in the shape of the blown plastic article to be produced, each mold half having adjacent its mold cavity an elongated narrow pinching wall interiorly defining an area of the article to be produced, one mold half having a pin receiving recess adjacent and outwardly of its pinching wall, at least one mold half carrying at least one penetrating plastic blank holding pin exterior to its pinching wall and adjacent the same and projecting above said pinching wall and adapted to engage and hold a plastic tube blank whilst the mold halves are open.

2. A mold assembly for blowing machines which consists of a mold adapted to blow closed hot plastic tube blanks consisting of two mold halves each having a cavity complementary with the second mold half in the shape of the blown plastic article to be produced, each mold half having adjacent its mold cavity an elongated narrow pinching wall interiorly defining an area of the article to be produced, and at least one mold carrying a plurality of plastic blank holding pins, each mold half being cut away adjacent its pinching wall and exterior of the latter for accommodation of said pins, the pins of one mold half bridging both said halves when the mold is closed and said pins being projected beyond the pinching wall of the mold half which carries them and adapted to engage and hold a plastic tube blank dropped upon said mold half when the mold is open and said cut away portionsbeing adapted to receive the end of a plastic tube blank pinched by said pinching walls when the mold is closed.

References Cited in the file of this patent UNITED STATES PATENTS 

